Antennas are used to transmit and receive electromagnetic energy. Typically, they are used within ambient temperature environments and are used in such devices as mobile phones, radios, global positioning receivers, and radar systems. Patch antennas, sometimes referred to as microstrip antennas, typically are an antenna design consisting of a metallization applied to a dielectric substrate material. Many such designs are constructed with printed circuit board etching processes common in circuit board manufacture. The geometry of the design is typically rectangular or circular, but other geometries are possible to provide enhanced performance such as increased bandwidth or directionality.
Additionally, microwave-based sensors have been developed specifically for use in high temperature environments. Next generation sensor systems are used in high temperature environments that require an antenna to be exposed to combustion gases. These microwave systems enable advanced control and instrumentation systems for next-generation aircraft and power generating turbine engines.
Sensors operating within the environment of a turbine engine are frequently required to survive in gas path temperatures exceeding 2000° F. for over 12,000 operating hours. Traditional patch antennas found in consumer, industrial, and military systems are not built of construction methods or materials that can survive a short period of time in such high temperatures, let alone survive and operate reliability for thousands of hours. Patch antennas have not yet been implemented in such harsh environments to date.
Radomes have been used as dielectric windows to protect antennas from the elements as well as extended temperatures during missile vehicle re-entry into the atmosphere. These radomes are typically large structures made from a low dielectric constant that allow electromagnetic energy to pass through with a minimum of attenuation. Radomes on missile re-entry vehicles typically have to protect the antenna on the order of minutes and will often use ablative coating and additional thermal management systems to lower the temperature of the antenna. Traditional radome approaches to improving the survivability of a patch antenna are not well suited for extended life applications.
Finally, the dielectric constant of substrate materials changes as a function of temperature. Since patch antennas typically operate as a resonant structure whose resonance is closely coupled to the dielectric constant of the substrate, the center frequency of the antenna can change as a function of temperature. This requires that the transmit frequency be appropriately changed to match the center frequency of the antenna in order for the antenna to radiate electromagnetic energy efficiently. Therefore, in order to reduce system complexity and the total transmit bandwidth of the electronics, it is desirable to minimize the shift in antenna resonant frequency as a function of temperature.
Implementing a long-life patch antenna for high temperature environments requires a different approach than that found in the prior art. Thus, a heretofore unaddressed need exists in the industry to address the aforementioned deficiencies and inadequacies.